1. Field of the Invention
This invention relates to processes for making vinyl caprolactam (VCL)-based polymers, and, more particularly, to a suspension polymerization process for making such polymers in water without requiring the addition of protective colloids, and which are obtained thereby as substantially odor-free polymers, without residual monomers, and in an environmentally friendly solvent.
2. Description of the Prior Art
J. Kroker et al, in U.S. Pat. No. 5,739,195, described a process for preparing an aqueous solution of 10-60% polyvinyl caprolactam (PVCL) homopolymer at a temperature above its cloud point in the presence of 0.1-20% by weight based upon vinyl caprolactam (VCL) monomer of a water-soluble synthetic polymeric protective colloid. Aqueous polyvinyl caprolactam homopolymer made with a protective colloid present in the starting materials was homogeneous, whereas protective colloid free systems were inhomogeneous, which were not readily dilutable with water except stirring for a prolonged period of time. Addition of an emulsifier to the starting material also formed an appreciable portion of PVCL polymer remained attached to the stirrer element.
Accordingly, it is an object of this invention to provide a process for making VCL-based polymers in water without requiring addition of a water-soluble synthetic protective colloid in the reaction mixture.
Another object herein is to provide a process of making VCL-based copolymers and terpolymers by suspension polymerization in which the monomers are fed into the reaction vessel at a predetermined feeding schedule.
Still another object herein is to provide an aqueous solution of VCL-based polymers which are substantially odor-free, monomer-free and uncontaminated by the presence therein of protective colloids.
A feature of the invention is the provision of an aqueous suspension polymerization process for making VCL-based copolymers or terpolymers wherein a suitable dispersing agent for the copolymer product is generated in-situ during the polymerization.
These and other objects and features of the invention will be made apparent from the following description thereof.